Carbonates such as ethylene carbonate, propylene carbonate and dimethyl carbonate are generally used as a solvent for dissolving an electrolyte salt for a non-aqueous electrolytic solution for lithium secondary batteries. However these hydrocarbon carbonates are low in a flash point and have high combustibility, and therefore, improvement in noncombustibility of a non-aqueous electrolytic solution is an important problem to be solved for securing safety especially in the cases of large size lithium secondary batteries for hybrid cars and distributed power source.
In order to improve noncombustibility of a non-aqueous electrolytic solution without lowering its performance, addition of a fluorine-containing solvent has been proposed (JP8-37024A, JP9-97627A, JP11-26015A, JP2000-294281A, JP2001-52737A, JP11-307123A and JP10-112334A).